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btrfs: fix the delalloc range locking if sector size < page size
Inside lock_delalloc_folios(), there are several problems related to sector size < page size handling: - Set the writer locks without checking if the folio is still valid We call btrfs_folio_start_writer_lock() just like it's folio_lock(). But since the folio may not even be the folio of the current mapping, we can easily screw up the folio->private. - The range is not clampped inside the page This means we can over write other bitmaps if the start/len is not properly handled, and trigger the btrfs_subpage_assert(). - @processed_end is always rounded up to page end If the delalloc range is not page aligned, and we need to retry (returning -EAGAIN), then we will unlock to the page end. Thankfully this is not a huge problem, as now btrfs_folio_end_writer_lock() can handle range larger than the locked range, and only unlock what is already locked. Fix all these problems by: - Lock and check the folio first, then call btrfs_folio_set_writer_lock() So that if we got a folio not belonging to the inode, we won't touch folio->private. - Properly truncate the range inside the page - Update @processed_end to the locked range end Fixes: 1e1de38 ("btrfs: make process_one_page() to handle subpage locking") Signed-off-by: Qu Wenruo <[email protected]> Signed-off-by: David Sterba <[email protected]>
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